Stp Mac Address Allocation - Cisco Nexus 9000 Series Configuration Manual

STP
This figure shows the 12-bit extended system ID field that is part of the bridge ID.
Figure 3: Bridge ID with Extended System ID
This table shows how the system ID extension combined with the bridge ID functions as the unique identifier
for a VLAN.
Table 7: Bridge Priority Value and Extended System ID with the Extended System ID Enabled
Bridge Priority Value
Bit 16
32768

STP MAC Address Allocation

MAC address reduction is always enabled on the device.
Note
Because MAC address reduction is always enabled on the device, you should also enable MAC address
reduction on all other Layer 2 connected network devices to avoid undesirable root bridge election and spanning
tree topology issues.
When MAC address reduction is enabled, the root bridge priority becomes a multiple of 4096 plus the VLAN
ID. You can only specify a device bridge ID (used by the spanning tree algorithm to determine the identity
of the root bridge; the lowest number is preferred) as a multiple of 4096. Only the following values are possible:
• 0
• 4096
• 8192
• 12288
• 16384
• 20480
• 24576
• 28672
• 32768
• 36864
Cisco Nexus 9000 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x
82
Extended System ID (Set Equal to the VLAN ID)
Bit 15 Bit Bit 13 Bit 12
14
16384 8192 4096 2048
Configuring Rapid PVST+ Using Cisco NX-OS
Bit 11 Bit Bit Bit Bit
10 9 8 7
1024 512 256 128 64
Bit Bit Bit Bit Bit
6 5 4 3 2
32 16 8 4 2
Bit
1
1